Polymers of cyclic olefins that contain the norbornene moiety can be made by ring-opening polymerization of the cyclic olefins in the presence of a metathesis catalyst comprising at least one alkylaluminum halide cocatalyst and at least one tungsten or molybdenum compound catalyst. Polymerization is accomplished by mixing a monomeric cyclic olefin, or a mixture thereof with or without other copolymerizable monomers, with a hydrocarbon solvent. A molecular weight modifier, selected from nonconjugated acyclic olefins, is then added to the reactor followed by an alkylaluminum halide cocatalyst and a tungsten or molybdenum compound catalyst. The solution polymerization reaction is conducted at 0.degree. to 200.degree. C., preferably 25.degree. to 100.degree. C., with stirring and is mildly exothermic. Polymerization time is on the order of less than 2 hours. The reaction mixture recovered directly from the reactor is a smooth, viscous polymer cement of honey-like consistency that comprises a polymer dissolved in the solvent.
Bulk polymerization is defined as polymerization in the absence of a solvent or a diluent. Early attempts of bulk polymerizations of the cyclic olefins using the metathesis catalyst system ended in failure because polymerization reactions were too rapid and therefore, uncontrollable. Furthermore, our initial bulk polymerization attempts resulted in materials that were very dark, had poor physical properties and poor appearance.
Our further developments in the bulk polymerization of cycloolefins led to another approach, which, likewise, was unsuccessful. This approach was characterized by splitting the monomer charge into two equal portions, one containing the catalyst and the other containing the cocatalyst. The object here was to mix the two portions of the monomer charge at room temperature and then transfer the mix to a heated mold where polymerization and hardening would occur very quickly. It was discovered that instantaneous reaction took place upon contact of the two portions whereby a solid polymer barrier was formed between the two portions of the monomer charge, encapsulating some of the monomer from each portion, indicating uncontrollable polymerization which prevented mixing.
This invention, therefore, relates to ring opening polymerization in bulk of at least one monomer containing the norbornene group or a mixture of such monomers or one or more of such monomers using a metathesis catalyst wherein an alkylaluminum halide cocatalyst is first transformed to at least one alkylalkoxyaluminum halide by reaction with at least one alcohol or active hydroxyl-containing compound but prior to subsequent contact (i.e., reaction) with at least one tungsten or molybdenum compound. The cyclic olefins can be formed into hard objects in a single step by means of a reaction injection molding (RIM) process. Examples of such objects are business machine housings, furniture, window frames, and the like.
The literature on solution ring opening polymerization of cycloolefins teaches the pre-contacting of at least one tungsten chloride catalyst with an alcohol or hindered hydroxybenzene for enhancement of polymerization efficiency, for increasing transition metal solubility, and for control of polymer microstructure (note U.S. Pat. Nos. 3,943,116 and 4,038,471) but specifically avoids pre-contacting the alcohol with alkylaluminum halide cocatalyst (note U.S. Pat. No. 4,239,874). Prereaction of the tungsten chloride with alcohol would allow for the formation of (RO).sub.n W, W=O or W-O-W bonds, and hydrogen chloride leaving the organoaluminum compound as a strong reducing agent for the transition metal with essentially no formation of alkoxyalkylaluminum halides. Excess amount of alcohol can be added to these systems at end of polymerization to destroy the polymerization catalyst and to coagulate the polymer.
Our discovery of prereacting alcohols and/or other active hydroxyl-containing compounds with organoaluminum compounds to retard polymerization at room temperature long enough to mix together the catalyst components, fibers, fillers and other additives and to pump the mixture into a mold, was completely unexpected and undisclosed. In fact, only very specific ratios of alkoxyl, alkyl and halide groups on the aluminum provide the conditions for stability at room temperature and rapid polymerization at elevated temperature.